QR codes

chartlet::qr turns text into a QR code. It is separate from the chart specification: there is no "type" for it and no CLI command, only the Rust API.

use chartlet::qr::{ErrorCorrection, QrCode};

let code = QrCode::encode("https://example.com", ErrorCorrection::Medium)?;
let svg = code.to_svg("Link to example.com", 4);

to_svg draws one unit per module with a quiet zone of the given width (four modules is the usual minimum) and sets role="img" with the title as the accessible name. Scale the SVG with CSS; shape-rendering="crispEdges" keeps the edges sharp.

A drawn example is in the showcase.

To draw the code with something else, read the modules directly: size() is the number of modules per side, is_dark(x, y) tells whether a module is dark.

What gets encoded

• Text is encoded as UTF-8 bytes (encode_bytes takes raw bytes), in the smallest version that fits, from version 1 (21 × 21 modules) to version 40 (177 × 177).
• The error correction level decides how much of the code may be damaged: Low about 7 %, Medium (the default) about 15 %, Quartile about 25 %, High about 30 %. Higher levels need a larger code for the same text.
• Of the eight mask patterns, the one with the lowest penalty score is used, so the same input always gives the same code and the same SVG bytes.
• Data that does not fit into version 40 returns DataTooLong with the largest length that would: 2953 bytes at Low, 1273 at High.